Ohmic Contacts for Phosphorus-Doped n-Type Diamond

Electric contacts for phosphorus (P)-doped n-type diamond films have been studied. The P-doped {111} homoepitaxial diamond thin films with n-type conduction are grown on high temperature high pressure diamond substrates by microwave-enhanced plasma chemical vapor deposition. The donor density and crystallinity of the phosphorus-doped diamond films were varied depending on the growth conditions. Metals with different work function and different reactivity to diamond films were deposited on the P-doped diamond films as electrodes. Ion implantation was also applied for introducing electrically active defects in diamond films. We found that n-type rectification properties with average Schottky barrier height of 2.4 eV were obtained from both Au and Cu contacts deposited on lightly doped diamond films with donor density ND of 5 × 1017 cm–3. Ohmic properties were obtained from electrodes on heavily doped layer with ND of over 1 × 1019 cm–3. Electrodes formed on the diamond film with electrically active defects also show Ohmic properties. These features indicate that the behavior of contacts formed on P-doped n-type diamond films is similar to those on typical n-type semiconductors.